Boiler Efficiency and The Whole System Approach

My gas bills are too high!!!’

‘My boiler is really efficient; it gets so hot in here’

These are extremely common complaints and comments we get from customers, particularly when carrying out annual servicing. But the actual definition of efficiency is quite different to what many assume.

First, let’s explore ‘Efficiency’, to quote Google:

‘The ratio of the useful work performed by a machine or in a process to the total energy expended or heat taken in.’

I get this may be hard to get your head around but in simple terms, for every unit of gas or electric we take in to our homes, we want as much of that to be used as possible and not wasted. An easier way to understand would be an older style light-bulb which many of us still have knocking around our homes. 

How many of us have burnt ourselves on a light-bulb that feels like it is hotter than the sun??? I have many times; in fact, I am sure there are many bulbs with bits of my skin melted to them. This is a prime example of poor efficiency. That light-bulb is lit by an electric current being passed through a thin coil of wire or filament, this thin wire has a high resistance and therefore it glows where it gets so hot, this is where the light comes from. Now you turned that light switch on to get light (funnily enough) but for each unit of electricity this light uses to actually give light, the vast majority of that electricity is actually being converted in to heat which is useless to the light process and thus wasted. After all, who has ever turned a light on because they are cold??

Therefore, we now use LED bulbs more and more because they convert much more of that electricity into useful light energy (which is why you switched the light on) as opposed to wasted heat energy. This is high efficiency.

Now, coming back to efficiency of our boilers and central heating. Efficiency is not measured by how hot your system gets, all systems should be capable of this and to be honest, efficiency of your system is a much bigger subject then just a new boiler which I will touch on but one step at a time. I am going to be using the next couple of blog posts to educate you all on some best practices such as to how this approach works and why we do things like this at FJM.

Efficiency is measured by how much of the gas we use is converted into useful heat and not wasted. An old boiler may get everything extremely hot, but some are less then 60% efficient. So, for every £1 you spend on feeding that old boiler gas, once it has been ignited and burned, 40p of that heat is not being captured and transferred to the water which is used to circulate around your system, it literally floats out of the boiler flue and in to the atmosphere never to be seen again. With new condensing boilers, most have a seasonal efficiency of 90% which in simple terms means, you would only be wasting 10p of heat for every £1 of gas you feed the boiler.

When the time comes for a new boiler, you may have looked at some makes and manufacturers and looked at how efficient they are. If you looked closely at the technical specifications, the efficiency figures are quoted as ‘Seasonal Efficiency’. This is a more accurate rating compared to the way older boilers were rated as this rating was arrived at via data gathering for a whole average year of average use. Efficiency of a boiler changes all the time depending on many factors such as water temperature in the system and how hard the boiler is working. 

As I have explained in a previous blog post, a condensing boilers efficiency comes from the condensing process. Condensing happens when the heat exchanger surface is at 55 degrees Celsius and below. When a condensing boiler is operating within a temperature range where it is condensing, it’s efficiency at that precise moment can often be above 100% and as much as 110% at times (Yes you really can get more out then you put in!!). Condensing releases heat back into the process but again this is a subject for another time. When it is not in this temperature range (i.e above 55 degrees), efficiency can be as low as 70% which is not much better than that old boiler you just said goodbye to. 

As I said further up, efficiency is much more then just a new boiler, it needs a Whole System Approach to really get the most out of a new condensing boiler. I am going to be using the next blog posts to gradually break this solution down which we use.

As they say, ‘Knowledge is power’. Here at FJM we work extremely hard on our knowledge. Many companies, large and small, spend millions on advertising how they can fit you a new fancy boiler for just £1500. I could go into a massive rant here at how crazy some of this is but I just have to remind myself that we do is in a different league to what these people offer and we achieve results which go far beyond what those offer at that price. When putting in a new boiler or even when servicing, we apply our hard-earned knowledge and take on this Whole System Approach to make sure your system, not just your boiler, is working as efficiently as possible. I can never over emphasize this point enough…. 

‘A boiler cannot work efficiently if the whole system is not set up to work efficiently together’ 

You can put a new huge powerful engine in a tiny car, if the other components are not set up or correct to work with the new engine, it won’t work efficiently and will likely break. However, if you also upgrade the brakes, tyres, gearbox etc etc, it will work. The same principle applies to your heating. 

So, do not always be fooled by someone who will just come and put you a new boiler in for a cheap price, it’s about the job you get. This is not to say a cheap job isn’t a good job, but a good technical engineer with thorough knowledge will pay for themselves in terms of efficiency, reliability and money saved in the long run.

I look forward to going into greater detail with you all over the coming weeks.

Take care and keep safe